Former Secretary of State Hillary Rodham Clinton strongly backs the Obama administration view opposing new Iran sanctions for now in a letter released by Senate Armed Services Chairman Carl Levin Sunday.

"At this moment it is of particular importance that our government's efforts work in coordination, not at cross-purposes. We should give anyone watching from Tehran no reason to doubt America's unity and resolve," Clinton wrote. "And should Iran fail to provide adequate assurances to the international community and undertake commitments to ensure it will not and cannot produce a nuclear weapon, then the legislative and executive branches will move with speed and unity, backed by America's allies to institute even tougher sanctions."

Clinton's letter to the Michigan Democrat is dated Jan. 26, just two days before President Barack Obama's State of the Union address in which the president reaffirmed that he would veto any sanctions enhancement legislation that reaches his desk as the negotiations continue with the Iranian regime.

Republicans advocating additional sanctions were quick to blast Obama's position after Tuesday night's speech. Sen. Ted Cruz, R-Texas, called the statement regarding Iran sanctions "one of the most dangerous things in the entire speech."

Coming from Clinton, the early favorite for the Democratic presidential nomination in 2016, the letter could help ice the sanctions bill. She noted her past support for enhanced Iran sanctions as a senator from New York.

"In my eight years in the Senate, I supported every Iran sanctions bill that came up for a vote and I spoke out frequently about the need to confront the threat posed by Iran's nuclear ambitions, its support for terrorism, and its hostility toward Israel," Clinton wrote.

In response to the letter, reported earlier Sunday by Politico , Levin called Clinton's perspective a "thoughtful, persuasive argument from an experienced, respected senior official."

"Her letter is another strong signal to Congress that we should not take any legislative action at this time that would damage international unity or play into the hands of hard-liners in Iran who oppose negotiations," Levin said in a statement.

Levin has long sided with the Obama administration on the sanctions question, along with Banking Chairman Tim Johnson, D-S.D. But Sen. Robert Menendez, D-N.J., the chairman of the Foreign Relations Committee, has been on the other side. The appetite for moving forward with sanctions seems to have diminished on the Democratic side, though many Republicans insist the measure should see a vote.